Snohomish County PUD has new plan for the Skykomish: no dam

The utility says the no-dam design is possible because of the unique geography of the river and would save $10 million. The estimated cost is $110 million to $175 million.

The Snohomish County Public Utility District has let the air out of its inflatable dam idea in favor of a “no dam” alternative that would tap water from an elbow in the Skykomish River near Index.

Officials say the proposal will cost $10 million less since it would not require a dam, weir or river barriers. The budget range is $110 million to $175 million.

“This project could be a valuable addition to our portfolio. Among the low-impact projects we identified in the past seven years, it's the lowest cost power source,” said Kim Moore, PUD assistant general manager of water, generation and corporate services, in a release.

The Everett-based utility says the no-dam design is possible because of the unique geography of the South Fork Skykomish River. A 180-degree turn creates a deep pool of water that can accommodate an underwater intake structure.

Water would flow from the upstream intake through a half-mile tunnel to a powerhouse that would be built next to the state's trap-and-haul facility that trucks salmon upstream above three waterfalls to 90 miles of spawning habitat. Two efficient turbines at the powerhouse would be able to power 22,500 homes.

New designs have modified the water intake area and fish screens to reduce the need for excavation by half and save six months of construction time.

The PUD says the project would leave enough water in the river for fish, recreation and aesthetics. It also would upgrade the aging trap-and-haul fish facility, and possibly make road and recreation improvements.

A PUD spokesman said the utility hired CH2M Hill for engineering and design work related to facilities such as the intake, tunnel and powerhouse, and improvements to the fish trap-and-haul facility. Environmental Resources Management was hired to do studies and surveys about aesthetics and recreation.

The spokesman said draft reports will be available in mid-summer and a final report should be ready in early 2015.

Construction could start as early as 2019.

Starting May 1, the PUD will survey its customers about the Sunset Fish Passage and Energy Project. The survey will cover public access, recreation, aesthetics and other background information. It will be at www.snopud.com/sunset.

The earlier proposal for an inflatable dam or weir near Sunset and Canyon falls was opposed by environmental groups who said the scenic free-flowing river should be preserved.

The Sierra Club, American Rivers and The Mountaineers organized a group called Save The Skykomish River.

In addition to the Sunset project, the PUD is assessing two other hydropower projects above Snoqualmie Falls near North Bend.